s390/pci: no msleep in potential IRQ context

The PCI instructions may be used in IRQ context so scheduling is forbidden.
Use udelay and shorten the delay since we are now polling.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>